1. Field of the Invention
The present invention relates to hairdresser's masking aids and in particular concerns masking sheets of the type that are adapted to engage and mask selected strands of hair while the selected strands are treated, for example, when performing a bleaching or a coloring process.
2. Description of the Related Art
A number of techniques are known that enable selected strands of hair to be treated and masked from unselected hair. For example, European patent number 0,122,145 discloses a hairdresser's masking sheet comprising a substrate of flexible material having an adhesive strip carried by the substrate for effecting attachments of the sheet to selected strands of a head of hair prior to treatment and for rapid removal of the strands from the substrate after treatment. The masking sheet comprises two rectangular panels, of substantially the same dimensions, which are welded together along a common edge to form a transversely extending hinge about which the panels are pivotal relative to one another. The hinged joint enables the panels to be hinged apart to receive the selected strands of hair between the panels and brought into proximity with each other to envelop the selected strands so that the strands may undergo a treatment process within the envelope so formed.
In one known example, the masking sheet comprises a first panel of opaque flexible sheet material, for example polyester, and a second panel of substantially transparent flexible sheet material welded to the first along a common edge. The transparent panel allows the hairdresser to monitor the progress of the coloring/bleaching process.
There are a number of drawbacks and disadvantages associated with hairdresser's masking sheets of the type described in EP 0122145. For example, the adhesive securing means (strip) becomes ineffective when brought into contact with many of the substances used to treat the selected hair. Consequently, the device tends to be labile, often slipping from the selected hair, thus requiring repositioning or replacement. Furthermore, the strips of adhesive material provide a barrier to treatment substances. Therefore, it is difficult to treat all of the selected hair within the envelope, particularly the roots of the selected strands that remain outside the envelope on the other side of the adhesive strip in use. Additionally, a problem experienced by hairdressers includes excessive application of treatment substances. For example, the application of too much treatment substance to the hair or to the interior of the envelope can lead to over processing of the selected strands, wastage of treatment substances and leakage of excess treatment solution from the envelope. The latter can be particularly problematic if excess treatment solution drips onto the clothing of the person undergoing the treatment process and causes bleaching or discoloration thereof. If too much treatment solution is applied and over processing occurs, the selected strands tend to tangle with neighboring strands when the treatment solution is washed out and the hair is dried.
This can lead to some of the selected strands breaking when subsequently combed. This problem arises from the fact that the hair cuticles become raised during over processing and the raised cuticles then interlock with the cuticles of neighboring strands, which causes tangling of the hair when it is dried.
Many hairdressers prefer to use strips of aluminum foil for masking strands of hair instead of using masking sheets of the aforementioned type. One of the preferred characteristics of metal foil is that it will dead fold to create a sealed region around the strands of hair being treated. Typically hairdresser's masking foil comprises strips of 18 micron aluminum foil. This thickness has been shown to provide sufficient strength for normal use and enables the hairdresser to reopen the packet or envelope formed by folding the foil to periodically monitor the coloration or bleaching process.
Metal foil is not, however, without its drawbacks. For example, a problem encountered by hair colorists and the like occurs when masking sheets of substantially opaque material, for example metal foil, are used to mask the selected strands of hair. Such opaque sheets do not readily enable the hair colorist to monitor the coloring or bleaching process without opening the envelope formed by the masking sheet around the selected strands of hair. This is an important consideration because as the hair grows out of the scalp it receives oxygen from the atmosphere and a hardening process known as keratinisation occurs. Keratinisation, or full keratinisation, takes about 6 weeks for normal hair, which is equivalent to about 25 mm (1 inch) growth. The first 25 mm of hair from the root is not, therefore, fully keratinised and more readily absorbs the active chemicals of the hair treatment substance used for colouring or bleaching. The remaining length of hair is fully keratinised and is hard and horn-like in texture. The greater hardness of the keratinised hair makes it much harder for the chemicals to penetrate the hair and this increases the amount of time required for the chemicals to be absorbed, which increases the process time. This is not necessarily a problem when highlighting selected strands by bleaching since the desired effect is to remove all pigment from root to tip and similarly where a whole head of hair is to be coloured darker than the hair's natural colour. However, the difference in processing times is significant when a whole head of hair is to be coloured lighter than the hair's natural colour and currently it is necessary for the hair colorist to first apply the treatment substance to the middle lengths and ends of the hair and wait for a predetermined amount of time, for example 20 minutes, before the same substance is applied to the roots in order to achieve even coloring. When using opaque masking sheets, such as metal foil, it is therefore, necessary for the hair colorist to periodically check that the roots have been processed sufficiently so that they are the same colour as the remaining keratinised part of the hair. As previously mentioned this involves the colorist periodically opening the envelope formed by the metal foil to observe the extent of the coloring process. In doing so, it is possible that treatment solution may escape.